JPH0240279B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to coal gasifiers, particularly slugging gasifiers of the entrained flow type.

A conventional entrain flow coal gasifier is described in U.S. Pat. No. 4,343,627. According to this prior art, a coal gasifier is operated by injecting carbonaceous material (including recycled coal) into its lower part together with feed air.

Combustion in this lower part of the gasifier then provides heat for the gasification reaction, and this temperature is maintained at such a temperature that the molten ash or slag can flow out through the slag tap opening in the bottom of the gasifier. be done. This portion of the gasifier, commonly referred to as the combustion zone, is operated near stoichiometric conditions to obtain maximum heat output and maximum temperature, thereby facilitating slag removal.

The combustion products produced in this combustion zone are conveyed upwardly to a reduction zone where additional fuel, which is carbonaceous material including pulverized coal, is added. This additional fuel is devolatilized along with the remaining carbon residue, called char, and reacts with the combustion products in the reduction zone to produce a combustible gas, which is a large amount of carbon monoxide. Gasification reactions are endothermic reactions that obtain heat from the combustion products produced in the combustion zone. The gasification process continues until a temperature of about 930°C (1700°C) is reached, at which point the gasification reaction is slowed down considerably for practical purposes.
The remaining char particles are then removed and then recycled to either the combustion zone or the reduction zone.

Thus, in the combustion zone it is desirable to obtain maximum temperatures in order to promote combustion of the solid carbon particles and to keep the slag as fluidized and free flowing as possible.

However, dissipation of heat from the combustion zone to the reduction zone reduces the temperature of the combustion zone.

For this reason, conventionally the wall section between the combustion zone and the reduction zone of the gasifier is bent inward to form a fairly narrow opening with a size on the order of 50% of the total gas flow area of the gasifier. It is known. Such a configuration, however, requires bending and spacing of the numerous tubes that form the walls of the gasifier.
There is a problem that manufacturing is troublesome and expensive. Moreover, since the spacing between the tubes changes along the length of the tube, there is also the problem that the spacing between the tubes becomes very fine.

Furthermore, conventionally, it has been known to inject fuel tangentially to a virtual circle within the gasifier, and to form a low-pressure flame core within the gasifier due to its centrifugal action. The presence of this flame core then tends to draw gas back from the reduction zone to the combustion zone. Such methods, however, not only result in undesirable cooling of the combustion zone, but also draw in the desired end products, ie, combustible gases, which are the carbonaceous materials that are being combusted in the combustion zone. The problem is that it burns out first.

The slag formed in the reduction zone, on the other hand, flows down along the furnace wall and then passes through an opening located in the center of the furnace between the reduction zone and the combustion zone to a position very close to the opening in the slag tap. Fall. This is because the temperature in the reduction zone is so low that the slag cools down considerably and cannot flow freely. Therefore, if such slag falls near the edge of the opening of the slug tap, a problem arises in that it promotes clogging of the opening of the slug tap.

As is clear from the above explanation. The following two-stage gasifier is desired.

First, heat dissipation between the combustion zone and the reduction zone is minimal.

Second, no gas is drawn back from the reduction zone to the combustion zone.

Third, the slag that falls from the reduction zone falls to an outer location within the combustion zone, i.e. a location far from the center, which allows the slag to heat up enough to flow freely before reaching the opening of the slag tap. To make things happen.

SUMMARY OF THE INVENTION The present invention therefore seeks to provide a two-stage coal gasifier that meets all of these desires.

A two-stage coal gasifier according to the invention includes a gasifier chamber that extends vertically, through which the gas flows upwardly, and has an opening for discharging the gas toward the upper end. A number of tubes forming the walls of the gasifier chamber form a slug tap opening at a central location at the lower end of the gasifier chamber. The lower part of the gasifier chamber is a combustion zone in which fuel injection means (nozzles) direct the carbonaceous material (coal), preferably tangentially to an imaginary circle inside the gasifier chamber. It is injected together with the supply air for combustion to obtain a heat source. On the other hand, the upper part of the gasifier chamber is a reduction zone, where additional fuel is input and gasified. A buttful is placed in the center between the combustion zone and the reduction zone. The baffle is larger than the opening in the slug tap and is positioned so that slag falling from around the buffle falls far from the opening in the slug tap.

This centrally located buttful minimizes heat loss from the combustion zone to the reduction zone and also isolates the central portion of the gasifier chamber between these combustion zones and the reduction zone to prevent gas from leaving the reduction zone. It prevents the slag from being pulled back toward the combustion zone and also forces the slag that falls from the reduction zone and enters the combustion zone far away from the opening in the slag tap, thereby removing the slag before it passes through the opening in the slag tap. This allows for sufficient heating.

DESCRIPTION OF PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, a two-stage coal gasifier 10 has a gasifier chamber 12 of circular cross section, which is divided by a buttle 14 into a combustion zone 16 and a reduction zone 18. ing. Combustion zone 16 is substantially cylindrical and is defined by a number of vertical evaporator tubes 20 . Water is supplied from the header 22 to these vertical evaporation tubes, and the water rises inside the evaporation tube to form an air-water mixture and is sent to the header 24.
From this header, the steam/water mixture is further fed to a steam/water drum (not shown) for steam storage and water recirculation.

On the other hand, the carbonaceous material-based fuel consists of recirculated coal or pulverized coal, which is combusted from a combustion injection nozzle 26 oriented tangentially to a virtual circle within the combustion zone 16. It is thrown into area 16. In addition, the combustion air is supplied to the wind box 2.
8. This air is often used as the combustion oxidant, but oxygen-enriched air or pure oxygen can also be used. Combustion zone 16 is operated at approximately stoichiometric conditions, in which the amount of air supplied into combustion zone 16 is close to the amount of air required for theoretical complete combustion. As a result, the combustion temperature within the combustion zone 16 is at its highest.

Combustion gas generated by such combustion passes upwardly through a space 30 provided around the baffle 14 and flows into the reduction zone 18 . Further, at the lower end of this reduction zone, additional fuel mainly composed of carbonaceous material containing pulverized coal is injected from the fuel injection nozzle 32. This coal fuel is deinterpolated and gasified while being subjected to an endothermic reaction, thereby producing combustible gas. This product gas passes upwards and then about 930°C
It flows out through the opening 34 at a temperature of (1700〓).
The ash contained in the coal is heated in the combustion zone 16 to form a molten slag, which is
Significant buildup occurs on the inner surface 36 of the walls of the combustion zone 16. And combustion zone 16 is about 1650℃ (3000〓)
Since the slag is operated at a set temperature of Injected.

This slag becomes sticky at low temperatures, and if left in this state, the slag will adhere to the opening 38 of the slug tap and gradually block the area around the opening 38 of the slug tap, so the temperature is always maintained at a high temperature. .

A portion of the ash produced in the combustion zone 16 is carried up into the reduction zone 18 and is further enriched by the ash produced by the combustion of the fuel injected from the injection nozzle 32. While a little slag fell onto the top of Batsuful 14,
Most of the slag is deposited on the inner surfaces 42 of the multiple tubes 20 forming the walls. The slag is then more sticky, but the combustion zone 16
It gradually flows down the wall into the interior. Sometimes the slag will build up on the walls, solidify into large clumps, and then fall off quickly.

The slag generated in the reduction zone 18 and falling down the center of the gasifier 12 flows down toward the outside by the baffle 14 located in the center of the furnace.
It then falls in an outward direction of the floorboard 44, ie, on the side remote from the slug tap opening 38. The slag will therefore have ample opportunity to be heated to an increased temperature and its viscosity will decrease so that it passes freely through the slug tap opening 38.

Both the fuel injection nozzles 26 and 32 of the combustion zone 16 and the reduction zone 18 are oriented tangentially to a virtual circle within the gasifier 12 to form a flame to promote mixing. ing.
Buzzful 14 tends to draw gas from reduction zone 18 into combustion zone 16.
The central core of the flame formed on the virtual circle is cut off.

And also, this Batsuful 14 is the combustion zone 1
6 to the reduction zone 18, thereby maximizing the temperature of the combustion zone 16.

As shown in FIG. 2, the buttful 14 is supported within the gasification chamber 12 by a hanger pipe 46 and reinforced by four shield/support pipes 48. The Batsuful 14, which is composed of a plurality of tubes,
Preferably, the bottom side is coated with a refractory layer 50 and the top side is coated with a refractory layer 52, such as silicon carbide. Additionally, a refractory layer 52 on top of the baffle 14 is shaped as shown to improve gas flow patterns and also to minimize particulate matter deposition on the baffle 14. In this way, the reason why it is okay to cover Batsuful with refractory material is that Batsuful does not absorb heat, but simply blocks gas, and must work in a high-temperature environment.
This is because only water cooling is required.

Water cooling for this buffer is provided by the header 54 (see FIG. 2), as shown in FIGS. 3 and 4.
This is obtained by passing water supplied from the pancake coil 58 through the inlet tube 56 and into the pancake coil 58. The water passing through this pancake coil then flows upward through the support tube 46 and
into the upper header 60 (see Figure 1). Such cooling water contains steam formed by being heated by gas during its flow, and therefore, this water/steam mixture is led from the upper header 60 to a steam drum (not shown). The steam is separated. Then, the water from which the steam has been separated is returned to the header 54 again. In this case, by making the water flow path a continuous upward path as described above, the possibility of steam generation in the water flow can be reduced. 5 and 6 show an example of a baffle 14 used in a gasifier 70 having a rectangular cross section. The baffle 14 is arranged within this gasifier 70 having a rectangular cross section. Batsuful 1
Cooling water for 4 is introduced from the inlet header 72 and flows through the serpentine coil 74 to the outlet header 76. Further, this baffle is covered with a refractory layer 78 on its upper surface and a refractory layer 80 on its lower surface. The baffle 14 is formed into a chevron shape as shown in FIG. 6, and a gas passage space 82 is defined around its outer periphery as shown in FIG.

As an example, the upward gas flow at the outlet of the gasifier is
It flows at a rate of ~9 m/sec (20-30 ft/sec).
By covering half of the gas flow area of this gasifier with a buffet, the gas velocity when passing through the space described above is approximately 30 to 46 m/sec (100 to 100 m/sec).
150ft/sec). This velocity value is much higher when the gas temperature is about 1650°C (3000°). It is also desirable that the baffle cover as much of the gas flow area of the gasifier as possible in order to block heat radiation from the combustion zone. However, the area that can be covered by the baffle is limited by the erosion effect caused by the high velocity gas, and therefore, in practice, about 50% of the gas flow area of the gasifier is blocked by the baffle.

Then, the size of the buffle is made larger than the size of the opening in the slug tap, and the buffle is placed directly above the projected area of the opening in the slug tap. The buffle thus extends laterally directly above and substantially beyond the slug tap opening. As a result, the slag dripping from the edge of the buttful is
Before flowing into the slug tap opening, it flows down far from the slug tap and is heated, increasing its temperature and lowering its viscosity, thereby minimizing the possibility of the slug tap opening becoming blocked.

As mentioned above, the gasifier according to the invention eliminates the possibility of cold gas in the reduction zone entering the combustion zone and backmixing, and also eliminates cooling of the combustion zone by heat radiation. A good shielding arrangement is provided which further facilitates maintaining fluidization of the slag in the area of the slag tap opening during operation of the gasifier.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing an example of a two-stage coal gasifier according to the present invention, FIG. 2 is a side view showing how the buttful is installed in the center of the gasifier, and FIG. is a schematic plan view of this Batsuful,
FIG. 4 is a longitudinal sectional view of this buttful, FIG. 5 is a schematic plan view showing an example of a buttful used in a gasifier with a rectangular cross section, and FIG. 6 is a schematic longitudinal sectional view of this buttful. . 10...Two-stage coal gasifier, 12,70...
Gasifier chamber, 14... Buzzful, 16... Combustion zone, 18... Reduction zone, 20... Numerous vertically extending tubes, 26, 32... Fuel injection means (nozzle),
38...Slug tap opening.

Claims (1)

[Claims] 1 a gasifier chamber which extends vertically and has an opening for gas to flow upward and to discharge the gas toward the upper end; a number of vertically extending tubes forming slug tap openings at the locations;
Combustion fuel injection means for injecting carbonaceous material at a low height position of the gasification furnace chamber; Reduction fuel injection means for injecting carbonaceous material at a high height position of the gasification furnace chamber; located centrally within the gasifier chamber at a height between the fuel injection means for use and reduction, and defines a reduction zone in the upper part of the gasifier chamber and a combustion zone in the lower part of the gasifier chamber. a buffle at an outer location of the gasifier chamber before the slag formed in the reduction zone flows to an opening in the slag tap at a central location at the lower end of the gasifier chamber. A two-stage coal gasifier that allows the coal to flow through it.